The state of the art includes processes of direct reduction which use the injection of hydrocarbons into the current of reducing gas to allow the reaction of reforming the methane in the furnace with the H.sub.2 O and CO.sub.2 in the gas; there are also known processes of direct reduction which use the injection of hydrocarbons with C&gt;5 directly into the furnace in the zone between the injection of the reducing gas and the outlet from above of the burnt gas.
From the following patent documents other processes are known for the direct reduction of mineral iron:
U.S. Pat. Nos. 2,189,260, 3,601,381, 3,748,120, 3,749,386, 3,764,123, 3,770,421, 4,054,444, 4,173,465, 4,188,022, 4,234,169, 4,201,571, 4,270,739, 4,374,585, 4,528,030, 4,556,417, 4,720,299, 4,900,356, 5,064,467, 5,078,788, 5,387,274, and 5,407,460.
The state of the art also includes processes wherein the hot metallic iron is produced in a reduction furnace of the shaft type, with a vertical and gravitational flow of the material, which is subsequently sent to the melting furnace by means of a closed pneumatic transport system in an inert atmosphere.